While the present invention may find application in a wide variety of tire testing apparatus wherein it is necessary to rapidly chuck tires it is applicable to great advantage in tire uniformity testing machines. Tire uniformity testing machines commonly include an upper rim, a vertically-movable lower rim, and a conveyor to bring a tire between the upper and lower rims. A mechanism is provided to raise the lower rim through an opening in the conveyor, carrying a tire with it, to the upper rim where the tire is inflated. The lower rim carries a center cone that is engagable with a center recess in the upper rim, the cone precisely positioning the upper rim with respect to the lower rim so that the two rims are concentric when a tire is clamped between them. A motor is connected to the upper rim to rotate it at a predetermined test speed. A load wheel or road wheel, rotatable on an axis parallel to the axis of the tire, is movable into engagement with the tire tread so as to load the tire as it rotates in a manner simulating a road condition.
A hydraulic actuator is connected to the lower rim to raise and lower it. This actuator must be capable of applying a force sufficient to overcome the separation force of tens of thousands of pounds acting on the rims when the tire is inflated. The force applied by the actuator must also be sufficiently great to hold the cone against the recess of the upper rim with sufficient pressure to driveably couple the upper and lower rims so that the rotational force applied to the upper rim is transmitted to the lower rim through the center cone rather than through the tire substantially without slip which might otherwise distort the tire and possibly affect test results.
A prior art apparatus and mechanism is described in U.S. Pat. No. 4,852,398.